Hardly. I have bunches of PSN games and I'm not shy about downloading things here or there. But I don't want it reaching any farther than it has. It's a nice alternative and works fine for smaller games nobody's going to give two shits about in 10 years, but by and large I want my primary game library to be a physical one, and I don't like it when I'm not given the option any longer.
And again, for me personally it would be a far, far bigger pain to swap out games to memsticks constantly rather than just carry a couple UMDs around. Generally I don't even do that, because these games are substantial and I'm usually only playing one at a time. The boxes and discs all stay at home, and the one game I'm playing stays in the PSP. If I happen to be fiddling with two at once, I just throw the extra game into my backpack and swap out as needed. I find that much easier than trying to keep multiple games on memory sticks, especially since I already use the sticks for tons of homebrew and emulation stuff.
The exception to this is when a game runs like shit off a UMD. You don't want to try playing Metal Slug Anthology from the UMD, because whoever programmed that game was a moron of the first degree. Seek times and load times are all kinds of terrible, to the point of extreme frustration, whereas running it from a stick negates those problems entirely. But that's the only game I can think of that was so botched I'd feel the need to run a copy rather than the disc. Most others are just fine.