If you haven't used a tablet extensively before, you'll never notice the difference in pressure levels. In olden days, tablets had far fewer levels, yet people still made great things. The Bamboo has 512 levels, which is hardly flint knives and bearskins.
I've had a few tablets over the year, and the main things I look for are:
1. The physical pen.
2. The ability to change the pressure curve.
If the pen doesn't fit your hand really well, it will become your worst enemy, and can literally cause pain. I have returned tablets in the past because of poor pen feel, and gone with a more expensive tablet. I have done this to get the pen, not because I needed advanced features of the tablet itself.
The other thing is whether the software will allow you to create non-linear curves for pressure sensitivity. I like to keep most of the change near the low end of the curve (light pressure). This gives the pen a "hair trigger", which takes getting used to, but without this I'd be in acute pain from hand strain in only a couple days.