Depends on what you want it for.

If you want to record speed and distance, and avoid getting lost, then what you have is perfectly fine. If you want street mapping capability I'm not sure whether the eTrex series will accept street maps?

If you're more concerned with fitness, then you'll want something that gives you heart rate and cadence, and probably compatibility with a power meter whenever one fits your budget. Most inexpensive bike computers will display cadence and often record average cadence, but point-by-point recording only comes with the more expensive units.

If you want a little bit of both, you could add on a small bike computer for a whole lot less money than a 705 would cost you.