Shade, your present version of the Celiran certainly looks better, though I still don't see the reason why their tail gives them +2 on Bluff checks to feint in combat, it's not a quality other races with flexible tails get. BTW, Sleight of Hand is the 3.5 version of what was called Pick Pocket in 3.0.
Also, just because I always feel the need to defend my judgment, if anyone mistook my version of the Celiran for being overpowered, they obviously over-estimated the usefulness of the prehensile tail and the tail slap. And underestimated the potency of the Dwarf and Elf in 3.5 and 3.0. The Celiran skill bonuses I gave were on-par with a human's bonus feat and skill points, while the Tree-Dwelling made up for their lack of a human's general flexibility, including multiclass flexibility (many people dismiss Favored Class as stupid or useless, but it does make some sense to me at least, and it does play a part in racial balance; some folks are just too used to playing one or two particular classes exclusively, and others are just too used to min-maxing any given class without multiclassing, but me and a lot of other folks tend to multiclass frequently and find the Favored Class mechanic to have weight; it's also important in official campaigns and such; I for instance am part of The 13 Kingdoms cooperative campaign setting, and both the games I DM and the games I play in using the T13K setting require adherance to the core rules and the setting's few additional rules).
Humans are sort of the low end of the totem pole in terms of racial balance, though they're better than half-orcs and half-elves at least, so my version of the celiran seems fine to me with its additional benefits of Prehensile Tail and Tail Slap..... Prehensile Tail only really lets them hold an extra item when it's convenient, but then that may prevent the tail from being used to grant certain racial skill bonuses as noted in my description for them. Since it can't wield a weapon or shield, and can't perform somatic components, it's only good for skill-boosting and idly holding items, though it does at least have use for wielding a wand, but so what; that doesn't mean the character could activate an extra wand each round, it still takes a standard action to use a wand. It does free up a hand for holding a weapon though at least, while the mage keeps their off-hand free to perform somatic components. The mage could always just take Simple Weapon Proficiency and wear a Spiked Gauntlet, then they don't need a free hand for a weapon, they could hold the wand in their gauntleted hand and use the other hand for somatic components. Not like Wizards don't already have feats to spare.
Tail Slap is quite average for a natural attack, and only slightly better than an unarmed strike for most characters. Celiran monks won't have much use for it, but it means other Celirans at least count as armed even when unarmed, and they can deal a bit better damage with the Tail Slap than they could with an unarmed strike, but no more than a dagger or something could do (well, a shortsword now that Celirans are apparently Small-sized), and unlike a dagger or shortsword, the Tail Slap can't be thrown, doesn't have a decent threat range, and can't be used normally during an iterative attack sequence. And it's certainly much weaker than any two-handed weapon. If you read anything at all about natural attacks in the Monster Manual or the System Reference Document, you'd know that natural attacks can't normally be used during a standard full-attack action unless the character uses only their natural attack sequence.
That means, for instance, that a 20th-level Celiran Fighter could, on a full-attack action, either strike four times with a weapon such as a Longsword at +20/+15/+10/+5, or he could strike just once at +20 with his Tail Slap natural attack. With my little caveat in the Celiran's Tail Slap description, though, I added an exception that lets them use their Tail Slap once during a normal full-attack action, as an additional secondary attack, rather than a primary attack. Thus it applies only one-half the Strength bonus to damage, if any, rather than one-and-a-half-times the Strength bonus to damage. And it's made at their full base attack bonus but with a -5 penalty for being secondary. Thus a 20th-level Celiran Fighter could get five attacks with a full-attack action this way, four of them at +20/+15/+10/+5 with a weapon, plus one Tail Slap at +15. It's like an alternate sort of Two-Weapon Fighting, except that the off-hand strike is a Tail Slap and there's just a -5 penalty with that attack roll, and no penalty on the other attack rolls that round. And there's no way to get extra Tail Slap attacks in a round, the Celiran is always limited to just one Tail Slap per round. Unlike Two-Weapon Fighting. And Two-Weapon Fighting works with weapons, which deal more damage or have better critical/threat stats than the Tail Slap does.
Tail Slap is, effectively, like a bonus Two-Weapon Fighting feat, only slightly different and marginally more useful to some characters. It's worth no more than 2 feats, tops. The way I handled Str to damage is just as per the MM/SRD dictates for critters with only one natural weapon. Except for the whole "secondary Tail Slap" thing that I added, which makes it useable similar to Two-Weapon Fighting, rather than the tail slap becoming completely useless once the character picks up a simple gauntlet or dagger. Most creatures in the Monster Manual, even such humanoids and monstrous humanoids as Lizardfolk, Centuars, and Troglodytes, have more natural attacks per round and/or better damage with them.