My Octavia vRS isn't doing too badly making two site visits a week up site access tracks to reservoirs (potholed an patched with 150mm stone). The tyres on it seem far more sensible than I had on the 3-series (M-sport touring) but then again I took that to the same sites.
I had loads of problems but to be fair to the car, many of them were self inflicted by buying a (relatively high spec) car at 140k miles ('04 320d touring with a stupidly long list of optional extras). For instance, I should've noticed that it was running cool when I bought it. I had to fit a new DMF/clutch (fairly unsurprising given the mileage), replace the thermostat (should've spotted this really) and replace the wiring loom (I'll let myself off on that one). Beyond that I had an awful lot of tyre issues that may or may not have been related to the alloys being quite old/knackered (combined with Sheffield roads). I traded it in for the Octavia at 198,950 miles (and looking on the DVLA website it's still going).I really like my Octavia (11 plate, ~100k miles). The boot is massive (I can easily fit loads of climbing gear and our quite large dog in the boot leaving plenty of space. Likewise, with the seats flat I can fit my bike in without issues. It'll come to the south of France in Dec with bike, dog and climbing gear and I can't see space being an issue. Undoubtedly the ride is less harsh and the massive lump of torque makes it a pretty 'lazy' drive. However, it's simply not as good to drive or as involved as the 3-series. I drove the 3 around Lancashire when house hunting in snow/ice and never found it impossibly bad but driving back from Kendal on one particularly wet day was terrifying (we passed an almost identical 3-series touring that had spun off into the central reservation). On long drives the 3-series was a nicer place to be with far less road noise and just a better level of finish all-round. I'd have bought another one but the boot profile slopes inwards both towards the back of the car and also from the roof which I thought compromised the space a bit too much (for the dog). I was probably wrong with this but the Octavia was far better value.