Earlier this week, a notable entry-level Raspberry Pi 5 PCIe HAT was released, supporting the PCIe 3.0 standard instead of PCIe 2.0 while also providing dual M.2 slots. The Seeed Studio PCIe 3.0 to Dual M.2 HAT [h/t CNX] costs just $45 per the official store page. For that price, you get one PCIe 3.0 lane per M.2 slot, with 8 GT/s throughput across both slots.
Besides the obvious use case of M.2 SSDs, Seeed Studio's Pi 5 PCIe 3.0 to Dual M.2 adapter is also intended for use with other devices, including AI accelerators, which also function within the form factor. Seeed Studio also notes that some SSDs may have compatibility issues, and lists some of its own drives as recommended companions. However, as CNX Software notes, your SSD should be fine as long as the ASMedia ASM2806 switch is supported.
Another compatibility concern, though likely a minor problem for much of the Raspberry Pi 5's target audience, is that you'll need to 3D print your own case for a Pi 5 setup with this adapter. It wasn't made to fit the default Raspberry Pi 5 case, unlike the official single-drive M.2 HAT.
So, does all that make this one a contender for the best Raspberry Pi 5 HATs? It's undoubtedly competitive for the price if you intend to increase throughput over the Raspberry Pi 5's default SD card, whose speeds are anemic in comparison. However, as CNX notes, if your tastes in storage veer more high-end, or if you have higher hopes for a proper mini NAS, the yet faster four-slot CM3588 computing module may serve you better.
In any case, this is a pretty nifty Raspberry Pi 5 HAT, and as the first one to use an ASM2806-based board. However, it remains to be seen how it will fare in the long run in a competitive market surrounding the Raspberry Pi 5.