Since I'm shopping only at around the $400 price point, unless I buy something used, I'm more interested in comparisons between the entry level scopes made by Rigol, Siglent, Owon, etc. No one has mentioned Owon customer service, but comparisons have been made between Rigol and Siglent. So while Rigol scopes (especially the DS1000Z series) may be great in many ways, if Rigol doesn't reply to emails, doesn't make firmware upgrades convenient to get, doesn't sell parts (did I understand that correctly?!), all this sure makes me hesitant about them. And is it correct that Siglent's customer service is better in all these areas? Being able to get help from the scope dealer (like TEquipment) instead of the scope maker might moderate these concerns, but I have no idea how much support the dealer can provide (certainly not firmware upgrades). If Siglent and maybe Owon do all the things which Rigol does not do, that's a ~major~ factor for me.
Frankly, I think you have your priorities wrong. When you buy bottom-of-the-barrel kit then you'll find that all manufacturers offer the same, absolutely minimalistic support, which at the end of the day means you can get repairs while the thing is under warranty and the occasional firmware update which may or may not fix relevant bugs. Yes, Siglent used to sell you replacement parts directly from China, but really, there's little point as during the warranty period the scope is covered under warranty anyways, and after that technology will have moved on so that it's rarely economically sensible to repair it. And Siglent can stop selling spares any day (they might have already), as they nowhere gurantee the availability of spare parts.
Yes, Siglent does offer firmware updates for download on their website. With no changelog, though, which means you have to guess which of the many bugs will be fixed in this update. And there will be bugs, as Siglent tends to throw products to the market long before the software side is at a reasonable level, and even then many issues remain unfixed for a very long time. Rigol on the other side doesn't offer firmware updates on their website but tends to send them to customers only when they have a specific problem. But at least on their popular scopes (DS2k, DS1kz) the Rigol software seems to be more mature than what I've seen from Siglent (aside from the fact that Rigol has the much better UI). Funny enough their more expensive scopes (DS4k, DS6k) are mostly neglegted and suffer from many issues that have long been fixed in the smaller models, but then I guess only very few buy these larger scopes when they cost as much as a comparable scope from the big brands.
Both Rigol and Siglent say that they are working on fixing the bugs, but none of them will give you a definite date as to when the fixes will be available (and if they give you a date then you will find that they won't hit it). However, some bugs may never be fixed.
That's about what you can expect. You can't expect after warranty care, you can't expect being able to buy replacement parts, or even to have the scope repaired when its out of warranty.
Which means you should spend less time worrying about the manufacturer support and look closer into getting a good scope (and I'd rather get a Rigol scope over a Siglent and Owon any day, as in the el-cheapo class they offer the best build quality and the best user interface of all three). Decide on a scope, and find a good dealer that is likely to be around for the length of the warranty period and which offers dealing with warranty issues, and you're set.
If you expect big name support you have to be prepared to pay big name money for it. Simple as that.