I happened to stumble across the "Routable garmin map" page on the wiki. Looks like routable OSM maps have been available for the last week and a bit. Interesting, I thought, so I duly loaded maps of the UK to my Garmin eTrex Vista. I already had a pretty good idea of where I was going this weekend, and the route I wanted to take, but I thought it would be interesting to see if they worked.

My personal feedback - I think it was giving perhaps too high a priority to "primary A-roads" - i.e. OSM trunk - compared with motorways.

It was trying to take me round the wrong way on 2 or 3 roundabouts. Perhaps this was a data issue however.

There were also times when it just ignored a few roundabout junctions - even if I was turning off what was the signed main route. Does it simplify some junctions for routing purposes - and just assume that you are travelling straight on?

Overall I would say it looks good - but there are some questions that need to be answered - e.g. how has it been done? Is it possible to create these yourself - perhaps with custom road styles or custom weightings for road types?

On the downside, the map I downloaded had "lock on road" set to on - and I forgot to turn it off until over an hour into my journey. As a result, I think that first hour of GPX trace will have to be deleted as useless (e.g. at one point I disobeyed it and carried on on the M6 rather than turning off - and the trace carries on up the sliproad until it realised I was still on the M6 - where it suddenly snapped back to the M6.)