No experience of the Satmap. But I think something like the Garmin eTrex range is a good choice and fairly popular among OSM mappers for on a bike.
Specifically the eTrex Legend HCx - you can add a memory card, which gives you loads of memory for recording tracks, and you can load OSM maps onto it.
And not too expensive (a fair bit cheaper than the Satmap anyway).
Some more details on the wiki: http://wiki.openstreetmap.org/wiki/Garmin
I was sort of heading in the eTrex HCx direction. Lots of good reviews by users and plenty talking about how good they are for creating data for OSM.
Problem is I am sucker for technology. I looked at the difference in the eTrex Vista HCx and the Satmap Active 10 in the shops to day and the screen on the Satmap looks about 4 times the size of the eTrex. I belive the Satmap is suppose to export data in GPX format so it surprises me no one talks about using it for OSM.
I recon I can get a Satmap attached to my bike for 300 GBP.
The eTrex Legent HCx works out at about 150 GBP
For both you can add a UK map for about 140 GBP but the Satmap version is a 1:50K (if only it was 1:25K) Ordinance Survey map against the eTrex TOPO maps that few people have anything nice to say.
For the amount I am likely to use it I think the eTrex Legend HCx will be my unit.
Er, don’t forget that you can add all kinds of OSM maps to the eTrex for free. This, as far as I know, is not something you can do with the Satmap. It’s somewhat of an overwhelming point in favour of the Garmin, if one of the primary purposes of the device will be to contribute to OSM.
If you really want more technology (and to spend more money), you could look at one of the higher-end Garmin devices, or consider getting an Android phone or something in addition to the eTrex. (The eTrex may not be as high-tech as other devices, but it’s terribly practical.)