Being a bit short of money when I had to replace my road STis I bought some Microshift 10 speed shifters. The quality was okay (considering they were only £100), but ergonomically they are generally pants. Its very difficult to drop the chain down the cassette when on the drops, and when on the hoods my mitts can get caught in the shift levers.
Based on that experience I have decided not to consider Microshift again, but to make sure I buy Shimano. Also don’t think I’d try the mountain bike shifters.
Apart from that I have no problems not being faithful to the big companies. Will happily use different brand chains, but do avoid Shimano as I went through a phase of snapping them. Tried a BBB cassette which was so heavy it nearly caused subsidence in my house (in my head).
I might actually be inclined to be more biased against ‘other’ brands if I find a fault, or possibly be less prepared to admit the bigger companies stuff can be short lived or just not very good. Does that make sense?