I have a H4n and it works find as an audio interface.
To avoid latency the H4n allows you to turn on monitoring in the hardware, so you can hear what you're playing with essentially no latency (headphones plugged directly into H4n. You always want to monitor from the hardware like this, regardless of interface, to avoid the annoying delay you get if you monitor via the round trip in/out of the computer.
The method for adjusting precisely for latency in Reaper is covered here: http://wiki.cockos.com/wiki/index.ph...erface_Latency
Basically, you set this once and forget about it. Once you set it, anything you record will automatically be offset by the latency amount so everything aligns auto-magically.
The H4n is perfectly acceptable for home recording projects. The pre-amps a bit noisy with the highest gain settings, but I only notice this with some microphones. For guitar or bass, they are fine.