Just took delivery of a Japanese N64. I've been putting this off for some time. The plan is to upgrade those PAL games that got butchered in PAL (M64, MK64, Pilotwings, Waverace64) and others that got some PAL optimisation but are still slower and it is significant (e.g. F Zero X).
The US and JPN machines are not region locked - it's just a physical limitation utilising tabs in the cart slot and casing - but my console came with a bridge adaptor that gets over these measures (it came with the US version of Rogue Squadron - not my thing but proves it works) so I'll be getting US versions in the main to avoid language diffs but will also be looking for those interesting (to me) JPN only titles like Sin & Punishment and Tetris 64 (with heart rate monitor!!)
Got Waverace 64 boxed (JPN version) too as I've never played it before. Always avoided the PAL version as it is reported to be a very poor port. It can look a bit rough in places (especially on an LCD panel - my CRT won't display in colour via s-video which is what the N64 pushes out unmodded which is a pity) but it plays extremely well. Very enjoyable game.
Good luck. I've personally found N64 games to be a blurry mess over RF or composite. When I use Svideo it makes a world of difference in terms of sharpness.
yep - s-video is the only viable option. I have been quiet surprised recently when messing about with my PAL N64 at how acceptable some games look on my 32" Sony Bravia. Some games look pretty good - some not so good. Overall the results are far better than I anticipated. It will be interesting when I get to compare PAL and NTSC versions of games to see if there is a difference re image quality AND speed.
Great decision. You'll enjoy the NTSC version much more!