[quote name='Esoteria']So, I just found out/realized that you can't just shove any old 2.5" hard disk in a 360, so now I'm wondering if an arcade is really good enough. I tend to play RPGs mostly. Will the lack of a hard disk be a problem for me? I'm not willing to spend the very ridiculous amount of money for 360 hard drives that I've seen thus far.[/QUOTE]
I'd research each RPG you want to play individually to see how the load times are without an install. If they are tolerable for you, then you should be fine.
That is unless you go nuts on XBLA games, music, movies, etc...