Mio? I have the 505 unit which is a bit pricy but comparable in price/tech level to the 1000. Mate has a Garmin and it does seem to throw a wobbly when in urban areas. The Mio is great to use, reliable (so far) and has some nice features like WiFi etc.
The route construction on the website can be a little irritating if you don’t get the settings right first (wants to direct you down odd cycleways rather than roads unless you turn that setting off).
Doesn’t use OS mapping though if thats important, which it may well be for mtb routes. Mine is mainly for road use.
Also, i had an issue with my original unit. Long story but had it one yr and it stopped obtaining satellite lock. Took it back to Halfords who buggered me around for a month before giving me a shop display model, which never worked properly. I contacted Mio direct, about getting it repaired and they came straight back asking for my address and would post me a brand new one no questions asked.
When it arrived it was the top of the range 505 with full European mapping and all the extra bits like cadence counter, HR monitor etc.
So, customer service is great.