One thing I don't like with 4E is that instead of ramping the martial powers up to the spell power, like Bo9S did, they toned the spells down to melee level. Even the dailies do not really look or feel impressive to me, not compared to spells of 3E, and powers from Bo9S.

You dirty old powergamer!
I think there are a few disadvantages to the "more power" approach.
One problem: You can give martial/non-spellcasting characters tons of combat power, but do you also want to give them the powerful utility power of mage? What's the martial equivalent to Teleport, Raise Dead, Scry?
Another:
The
nd6 points of damage per level and the "Save or Die" effects of "traditional" spells just makes hit points irrelevant, since they scale at the same rate. You could go with a "wound point" system. Everyone can take Constitution Score (+class bonus) boxes of damage, and a fireball deals 1d6+INT boxes of damage in a 20 ft burst, while a longsword deals 1d8+STR damage to a single creature.
Sure, you lose out the relative power difference between 1st level and 10th level in hit points, but you could still keep the to-hit and defenses changing with level, so the difference will still be very strong. The system might get swingier against lower level opponents then using traditional HD (two lucky rolls can kill a high level PC), but the real problem is that the system is always swingy against equal level opponents. (Two average rolls can kill an equal level PC)
If you don't do this, you will begin comparing 1d8+STR longswords (or magic missile) at-wills with 10d6 fireball dailies (or "Brutal Strike" fighter daily). And you will notice that the fireballs and brutal strikes will over-shadow the rest, and they are still too precious to not recover at first opportunity.
Just having to chose between 1d8+INT vs 2d8+INT vs 3d8+INT powers makes dailies (and encounters) less critical. They are important, but you don't want to use them every time.