Pretty much everything that you've seen above is spot on. GURPS combat is, for the most part, much deadlier than d20 combat. However, you have a choice as to your complexity level and implementation. GURPS specifically offers a Basic and Advanced Combat options...and the Basic options is more than adequate for most situations (I used it for a Supers game for 8 years). The Advanced system is much more miniatures focused (though it doesn't require them) and if you can handle combat in d20, you can handle the advanced rules. The biggest difference in GURPS is that successfully hitting is only half the battle...if the target is good at parrying, using their shield or just moving fast, you may still miss. If they have suitably 'turtled up', then you might not harm them, even if you hit.
As a skills & Advantage based system, GURPS offers a huge amount of flexibility and customizability to both players and DM. However, the system has some flaws that need to be accounted for. First, only two of the four stats are truly valuable for most character concepts. IQ and DX are the roots of most feats, and as such, more valuable than ST and HT. The system of 'defaults' assures that a character with high DX has a reasonable chance of succeeding at many skills, and some advantages, like Eidetic Memory, were just plain broken. The character creation system requires that GMs be involved heavily, as many of the advantages require judgement calls. Since characters take disadvantages to gain points, some things have to be monitored...for example, anosmia (no ability to taste/smell) or being colorblind are popular choices. Good DM's can make these REAL disadvantages, of course, but in GURPS, you need to be more dilligent at creation time.
There are other things that are more of a 'taste' issue. Some things, such as the default magic system, are either a boon or a bore, depending. Characters never truly become immortal gods, without the help of cinematic rules (of which they present a great deal). Many of the mechanics come across as arbitrary, and need examination to make sure they actually make sense (d20 is greater as far as internal consistency is concerned, although prior to the release of 3E, I wouldn't have said so).
GURPS, overall, is extremely flexible, and is nice in that it allows you to use one system for many different settings (hence the reason it was system of choice for GURPS Japan, Supers, Fantasy, Anime and a few other homebrews, such as my personal GURPS Falkenstein). It's also excellent in that 'wacky' character concepts are much easier to execute. I once had a character who was named Jack (as in 'of all trades') who was just lucky (via the Great Luck advantage) and had a high DX, with few points spent on skills. He was fun.

The same system allowed me to create a 30's Irish-descended beat cop in a GURPS Cthulu game, a hard-bitten street-fighter named 'Viper' in a GURPS Bloodsport game, and a schmuck who could create elemental automaton doubles of himself in GURPS Supers. Like I said, flexibile.
