The latest issue of Practical Sailor has a review of handheld non-cartographic GPS units.
Prices have levelled out on GPS units lately. There also doesn't appear to be a whole lot of difference between them. They all perform the same basic functions. They're all equally accurate and waterproof.
The ratings were based mainly on ease of use and readability.
The top rated one was the Garmin GPS 76 ($183)
The runner-up was the Magellan SpoTrak Pro Marine ($250)
Of the more inexpensive models, they liked the Cobra GPS100 ($92)