I wouldn't go buy a new microwave just to spite the brand. For one, Frigidaire isn't significantly less reliable than the other major appliance brands - they have noticeably worse "fit and finish" in their build quality (I don't think I've ever seen a Frigidaire Pro badge that was on straight, ever. Their french door freezer doors will not line up with even perfectly adjusted fridge section doors. etc.) but also typically a lower price point. Just about all appliance companies make some shit-boxes - from stats I've tracked at work, the common consumer brands in the US have roughly 10% failure rate for the first year, and about 30% failure rate over 5 years. Those rates stay pretty consistent between brands (as soon as someone looks like they are going to upset the balance, they release a fancy new design for an ice maker or something that just shits all over the bed and has to be 'service-bulletin'ed to consumer reports hell and the stats wander back into line).

Basically, if the thing is working now, I'd keep it until either it doesn't work or you just really want/need some feature it doesn't have. Buying a new appliance is just going to be giving money to a different-but-still-shitty brand.