It's a huge upgrade, IMO. You'll see - once you really get the hang of the PM process, your beers will taste tremendously better. My personal opinion is that it's really difficult to tell the difference between a well-made PM brew and an AG one, all other things being equal. This is especially true if you do a full boil, but I've made some PM/partial boil brews that are better than many commercial brands, IMHO.
It's really all a matter of technique. I highly recommend DeathBrewer's method, since it's so simple and so effective. I can regularly get 70% efficiency with it, mashing about 8 lbs of grain or so, and making up the rest with LME or DME.
Of course, you still have to take care of the whole process - make sure your temps are right throughout, pitch a proper amount of yeast, regulate fermentation temps, etc. But if you do you'll see a major jump in the quality of your final product.