Panowie, ale o czym my mówimy? Jakie to C64? Toż to zwykły PC, nic więcej :(

C64 emulation issues (for the DTV2/3)
CPU
PLP/PHP: sometimes bit 5 in the CPU status register is unset
CIA
TOD (time of day) timer is missing ($DC08-$DC0B/$DD08-$DD0B)
Keyboard emulation is flawed (writing to $DC00 and reading from $DC01 works but not the other way around)
The original CIA has a one-cycle latency between writing to the register and outputting the data on its port pins. The one in the DTV is faster, leading to problems with certain fastloaders (PETSCII posting)
SID
filters are missing (plus some other minor SID changes)
there is a number of flaws (see "DTVSID research" thread on PETSCII and VICEplus test programs)
no POT lines (paddle)
NMI timing is not accurate
Some illegal OPs are missing, some guesses at what they do instead:
SHS ($9b) is a nop absolute,y
DCP ($c7) is zeropage, read modify write, decrement and compare against the accumulator
ANC ($2b) it a 2 byte nop
($fc) is a nop absolute,x
VICII
idle fetch is different (see _draw_idle in VICEplus vicii-draw.c), leading to deviant behaviour in screen border
DMA delay has a fixed delay of one, breaking Variable Screen Positioning (VSP)
$D019 bit 7 is (bit 0 | bit 1 | bit 2 | bit 3) and gets set even if these conditions were not enabled in $D01A (and, thus, didn't actually trigger an IRQ)
Reading $D01E/$D01F does not clear the corresponding $D019 bits - in contrast to the C64, these are sticky and have to get ACK'd explicitly.
Misc Hardware Issues
PAL output signal is known not to work with some digital displays (flat panel displays, FBAS=>VGA converters, TV cards, ...). Setting $D04E to 2 or 3 seems to help sometimes (PETSCII thread)
PS/2 keyboard acts strange after powerup (after a reset everything is okay though). F7 key does not work; shift keys are swapped. See here for possible fixes

How compatible is the DTV with the C64?
The DTV has a few but crucial emulation issues. Many games (say, 10 to 30%) do not work properly. Old games are just as susceptible not to work as are newer ones: For example, Bruce Lee does not work without patches at all (but was easy to fix) while Mayhem in Monsterland 'just' has graphical glitches (that were very hard to fix). See also DTV Patched Games.